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Analysis of the net addresses where the e-mail messages originated showed that more than 100,000 hijacked home computers spread across 119 nations had been used to despatch the junk mail.
To try to beat anti-spam techniques that look up the net address from which spam originates to see if it that location has a reputation as a spammer, many of the machines used to send the mail had been recently hijacked. Analysis showed that many had only been taken over in the last 30 days, said Mr Peterson.
"We ran the sources of this and found out a massive distribution of countries," Mr Peterson told the BBC News website, "it's very much centred in Europe."
This widespread, sophisticated infrastructure involved more than 1500 web domains that acted as the web shops for the drugs advertised in the junk messages.